Implantable medical devices for producing a therapeutic result in a patient are well known. Examples of such implantable medical devices include implantable drug infusion pumps, implantable neurostimulators, implantable cardioverters, implantable cardiac pacemakers, implantable defibrillators and cochlear implants. Of course, it is recognized that other implantable medical devices are envisioned which utilize energy delivered or transferred from an external device.
A common element in all of these implantable medical devices is the need for electrical power in the implanted medical device. The implanted medical device requires electrical power to perform its therapeutic function, which may include driving an electrical infusion pump, providing an electrical neurostimulation pulse or providing an electrical cardiac stimulation pulse. This electrical power is derived from a power source.
In some implantable medical devices electrical power can be transcutaneously transferred through the use of inductive or RF coupling. For instance, this can be accomplished by inductively coupling a primary coil that is external to a living body with a secondary coil that is coupled to, or included within, the implantable medical device. Current induced in the secondary coil is used to store energy in a rechargeable battery or capacitive element and/or to power the implantable medical device implanted within the body. In this form, an internal power source such as battery or capacitive element can be used for direct electrical power to the implanted medical device. When the power source has expended, or nearly expended, its capacity, the power source can be again recharged transcutaneously via inductive coupling from an external power source that drives a primary coil that is temporarily positioned on the surface of the skin.
Devices and techniques have been developed to provide transcutaneous energy transfer in order to power an implantable medical device and/or charge or recharge a battery associated with an implantable medical device. As previously noted, techniques generally employ a primary coil driven by an external power source.